The optical subscriber terminal is a customer premise equipment (CPE) that aggregates and transports both Ethernet and time-division multiplexed (TDM) customer traffic to and from a network routing device and the network beyond. Customer Ethernet traffic may include data at 10 Mb/s, 100 Mb/s or higher rates from customers' Ethernet local area networks, while TDM data may consist of data at DS3 (or STS-1) and T1 speeds. The customer traffic is aggregated into an optical uplink for transmission to the network routing device.
Typically, data from the Ethernet ports are multiplexed at the physical layer into multiple respective SONET STS-1 synchronous payload envelopes (SPEs) as a serial data stream. The serial data stream is converted into a SONET optical signal for transmission to the network routing device. The network routing device demulitplexes the serial data stream to recover data from each individual Ethernet port for processing by higher layer network equipment such as routers. This conventional method is inefficient in bandwidth utilization, because the data from each port is mapped into its respective SPE. The conventional method also requires substantial processing in the higher layer network equipment such as routers.